Answer:
0.375, or 3/8
Explanation:
This is binomial probability, with n = 4, x = 2 and P(tails) = 0.5.
Using a calculator with probability distribution functions built in, we evaluate
binompdf(4,0.5,2) = 0.375
Thus, P(exactly 2 tails) = 0.375, or 3/8